As the use of touch screens, such as for public information kiosks, portable devices, and gaming applications and the like, increases, so does the need for more durable touch screen designs. Use of lamination configurations is a known technique to enhance durability of and add features (such as conductive, anti-glare, and anti-reflective coatings) to the touch screens. For example, using a transparent, conductively coated flexible plastic material, such as transparent conductively coated PET laminated to ultrathin glass (having a glass thickness preferably less than about 0.3 mm in thickness, more preferably less than about 0.2 mm in thickness, most preferably less than about 0.1 mm thickness) as the top sheet in a conventional resistive touch screen design (as shown in FIG. 1) is known in the art of touch screen manufacturing. The coating of flexible PET with a transparent conductive coating, such as by a web coating process, is also common process knowledge.
Typically, touch screens, and in particular capacitive touch screens, are manufactured via a multi-step process that includes multiple high temperature curing stages. For example, a touch screen may be manufactured by first washing a piece of flat glass, screen masking the glass surface where no conductive coating is desired and coating the glass surface with a transparent conductive coating, such as antimony tin oxide (ATO). The transparent conductive coating is then often fired at a high temperature of about 510 degrees Celsius or higher to improve properties thereof. The coated glass substrate is then washed and a conductive electrode, such as a silver conductive epoxy or paste portion, is printed onto the surface and then this is cured at a high temperature, such as about 480 degrees Celsius or higher. The glass is washed again and a hardcoat layer (such as an inorganic oxide, such as silicon dioxide) may be coated, such as by spraying, onto the glass, or the glass may be dipped into a precursor solution of the hardcoat coating. The hardcoat is then cured at a high temperature, such as about 520 degrees Celsius or thereabouts. A protective border layer may then be screened over the silver and may then be cured, such as via an ultraviolet (UV) curing process or, where a glass frit may be used, via another high temperature firing process. The glass is then cut to its final size and the edges are seamed before the touch screen is washed and packaged for shipping. The conductive coating is preferably antimony tin oxide due to the stability and uniformity of ATO during the multiple heat curing processes. Examples of such coatings and sensors or touch screens are described in U.S. Pat. Nos. 6,488,981; 6,549,193; 6,727,895; and 6,842,171, which are hereby incorporated herein by reference in their entireties.
It is known that in interactive information devices such as touch panels and pen-input devices, there is usually at least one rigid glass substrate coated with a transparent conductive coating such as indium tin oxide (ITO) or doped tin oxide. Depending on the coating deposition process, the transparent conductive coating may need to be further oxidized to achieve optimum transparency and further reduced to achieve optimum electrical conductivity. This curing process requires elevated temperature in a forced dry air environment followed by the introduction of an inert atmosphere forming gas. It is also known that in interactive information devices such as touch panels and pen-input devices, there are usually thick film electrode patterns deposited on the conductive films. These thick film electrode patterns, typically silver frit compounds, also need to be thermally bonded to the conductive thin film and the glass substrate under the conductive thin film.